Abstract : The modular setback pin (MSP) was designed to operate in both the timer and trigger of the M557 mechanical time fuze. The device senses all standard gun firing environments and differentiates between them and handling shocks, including drops of 40 feet and higher. Further, the unit locks in the functioned position (down) after the setback pulse ceases. This prohibits the setback pin from interfering with the operation of the spin detent. A computer-aided study to determine the time required for the MSP to function under various setback loads is described in this report. A modified version of this program determined the relative importance of nine design features as they relate to drop height. Limited physical testing was also conducted. A study and conceptual layout of automated assembly and testing equipment for the MSP are also described.